1. LCLS-II Transverse Tolerances Tor Raubenheimer May 29, 2013

2. LCLS-II FAC Review, February 27-28, 2013 LCLS-II Accelerator Parameters Slide 2 parametersymbolnominalrangeunit Electron energyEfEf 13.57.0 – 13.5GeV Electron bunch chargeQ0.1500.01 - 1.0nC Pulse repetition ratef120SS, 1 - 120Hz Transverse slice emittance  x,y 0.40.15 - 1.2 mm Peak currentI pk 3.00.5 - 5.0kA Slice energy spread EE 1.40.1 - 1.5MeV

3. LCLS-II Acc. Phys, May 29, 2013 Tolerance Specifications Transverse tolerances to minimize emittance dilution, optical errors and beam jitter  Tolerances based on most stringent conditions – usually 10 pC with 0.17 mm-mrad emittance and over-compression with 0.5%  E/E  Sources include alignment errors, magnet harmonics, PS fluctuations, component vibration, and coupling from other sources  Jitter tolerances set to limit beam motion to 33% rms in undulator from all sources  All tolerance specifications are rms values Full tuning / bump studies not completed Slide 3

4. LCLS-II Acc. Phys, May 29, 2013 Transverse Jitter Sources Based on  = 0.15 mm-mrad, N = 250 pC,  E/E = 0.5% and  <33% Slide 4 (  I/I = 15%)

5. LCLS-II Acc. Phys, May 29, 2013 Comparison with LCLS-I Tolerances LCLS-I quad jitter tolerances were specified to limit the beam expected amplitude to 10% of the rms beam size.  The amplitude is sqrt(2) larger than the rms offset LCLS-II tol. are specified for 33% rms jitter from all sources Although not specified, it looks like LCLS-I tolerances were specified for 1 mm-mrad versus 0.17 mm-mrad for LCLS-II  LCLS-II total jitter budget is ~2x looser Quadrupoles are small fraction of jitter budget  quadrupole jitter requirements are 1.7x tighter Slide 5

6. LCLS-II Acc. Phys, May 29, 2013 Current and Energy Jitter  Transverse Beam current jitter couples to transverse jitter through transverse wakefields and CSR Beam energy jitter couples to the transverse jitter through residual dispersion, coupling to wakefields in dispersive regions and changes in phase advance Slide 6 Longitudinal Wakes for 250 pC, 3 kA CSR Cancellation Septum kick for 250 pC, 3 kA

7. LCLS-II Acc. Phys, May 29, 2013 Steering Correctors Largest potential source of beam jitter at ~20%  X,Y/  X,Y  MCOR power supplies limited to ~1e-4  I/I  LCLS-I specified 3e-5 toelrances for many dipole correctors Sizes of MCORs reduced to balance corrector strength to reasonable values  ease tolerances Used ‘reasonable’ maximum quadrupole alignment errors and compared to typical LCLS-I corrector strengths Slide 7

8. LCLS-II Acc. Phys, May 29, 2013 Steering Correctors (2) Slide 8 L1 / L2 values are < 10 G-m L3 values < 20 G-m BC2 values large

9. LCLS-II Acc. Phys, May 29, 2013 Steering Correctors (3) Maximum quadrupole misalignments for corrector sizing Slide 9

10. LCLS-II Acc. Phys, May 29, 2013 Steering Correctors (4) Most correctors could correct a local large misalignment  In some cases, multiple (2) correctors will be required Slide 10

11. LCLS-II Acc. Phys, May 29, 2013 Steering Correctors (5) Not showing Tables – look in PRD! Most correctors much weaker than in LCLS-I specs but similar to LCLS-I operating values L1 / L2 / L3 correctors are all much weaker than SLAC linac LTU sized at 60 G-m and dump correctors are 120 G-m Slide 11

12. LCLS-II Acc. Phys, May 29, 2013 Dipole Magnets (1) Achromatic magnet strings should be largely insensitive to power supply fluctuations  In practice, magnets are only matched at 1% level and include +/- 1% trims to match magnets Power supply regulation tolerances calculated to limit (1) change in path length, (2) transverse trajectory in achromat, and (3) transverse jitter due to 1% magnet mismatch  Dipole string PS are medium PS with 5e-5 regulation  Trim power supplies are standard MCORs with 2e-4 regulation Slide 12

13. LCLS-II Acc. Phys, May 29, 2013 Dipole Magnets (2) Roll jitter tolerances vary between 1 and 10 urad  Dipole roll jitter is 2 nd largest  Y/  Y jitter source Roll alignment tolerance is set to limit dispersion errors and trajectory  Dipole roll alignment tolerances vary between 0.3 and 5 mrad These may be overly tight and can iterate as needed Slide 13

14. LCLS-II Acc. Phys, May 29, 2013 Quadrupole Magnets (1) Quadrupole vibration tolerances are the 3 rd most important source of beam motion  Typical values vary between 100 and 50 nm Quadrupole alignment set loosely by increase in projected beam sizes  Typical values range bewteen 300 and 100 um  Without bumps  ~ 500% Slide 14

15. LCLS-II Acc. Phys, May 29, 2013 Quadrupole Magnets (2) Quadrupole vibration tolerances tight in BC1, BC2, Bypass extraction and LTU – typical jitter contributions <1% magnet May want to work on S20 quadrupole supports Slide 15 S20 and Bypass extraction LTU BC1 BC2 Vibration Tolerance [um]

16. LCLS-II Acc. Phys, May 29, 2013 Quadrupole Magnets (3) Quadrupole power supply regulation tolerances are calculated to minimize (1) , (2)  *  E /E, and (3) jitter due to trajectory errors: 3e-5  I/I minimum tolerance For jitter calculation assumed quadrupole center-to- trajectory of 100 um in BC2, Bypass ext. & Undulator; 200 um in BC1 & LTU; 1000 um in Bypass; 300 um elsewhere Slide 16 Bypass extractionLTU Arc

17. LCLS-II Acc. Phys, May 29, 2013 Transverse Tolerances Alignment Tolerances Alignment numbers provide guidance  beam-based tuning Slice  impact is small (slice = 1% of  Z ) Projected  impact is large Calculated for over-compressed case with 0.5%  E/E Alignment: 300 um on rf structures and most quadrupoles; 200 um in BC1 and LTU; 100 um in BC2, Bypass and Undulator  X-band structure transverse wake is 40x larger than S-band yielding 30% projected  growth by itself Slide 17 HXR (Proj)SXR (Proj.)  X /  X  Y /  Y  X /  X  Y /  Y 428%496%502%590% (slice  are ~2%)

18. LCLS-II Acc. Phys, May 29, 2013 Magnet Field Tolerances Detailed magnet tables for all dipoles, quadrupoles and steering correctors Multipole tolerances calculated using 250 pC (0.5 mm-mrad) over-compressed beam (0.5%  E/E) plus steering errors of 0.5 mm except 1 mm in injector, bypass and undulator Multipole tolerances are relatively loose except where there is dispersion  Uncorrelated effect on beam core is small <5%  and  <0.1%  K/K Slide 18 Partial table for SXR LTU quads